CONTROL OF ORGANIC MATTER FROM SURFACE WATER IN THE COASTAL AREAS USING A HYBRID COAGULATION-MEMBRANE SYSTEM
Keywords:Surface water, Hybrid coagulation-UF, THMs formation, Salinity impact
With the impact of climate change, it is impossible for the residents living in coastal areas to employ underground water due to the severe salinity intrusion, they switch to using surface water instead. Nevertheless, the surface water source often has high organic matter, turbidity, and occasionally gets salinity, which results in difficult and costly treatment. This paper evaluated the efficiency of using a hybrid coagulation and ultrafiltration (UF) process in treating surface water in coastal areas of Vietnam. A series of preliminary jar tests were conducted to optimize the pH condition, coagulant dose, and impact of salinity on turbidity and organic matter control. The tests with the hybrid coagulation-UF system were tried after that and fouling evidence was investigated. The jar test results rendered that pH of 6.5, Poly Aluminum Chloride (PAC) with a concentration of 10 mg/L, and pre-chlorination with 10mg/L NaOCl solution were the best conditions for UF pretreatment. Salinity influenced the coagulation process, not the membrane one. The removal efficiencies of turbidity and total organic carbon (TOC) removal were 88% and 66% after coagulation, and 95% and 67% after the hybrid processes, respectively. The presence of trihalomethanes (THMs), specifically, Chloroform, Dibromochloromethane, and Bromodichloromethane were detected in the disinfected water, but much lower than the standard. The THMs formation depended on the contacting time and chlorination doses. The proposed system initially showed some promising results in controlling the pollutants of this river source in the coastal area. Future studies would look at thoroughly the impact of salinity on THMs formation for this kind of water.